1-{2-[(2,4-Dichlorobenzylidene)amino]ethyl}-3-methylimidazolium hexafluorophosphate

In the title Schiff base compound, C13H14Cl2N3 +·PF6 −, the dihedral angle between the aromatic ring and imidazole ring in the cation is 6.10 (2)°. Intermolecular C—H⋯F hydrogen-bonding interactions and π–π stacking interactions [centoid–centroid distance = 3.7203 (12) Å] help stabilize the crystal packing.


Comment
Ionic liquids are attracting much interest in many fields of chemistry and industry, due to their potential as green solvents for a wide range of applications in synthesis, catalysis, electrochemistry, and liquid-liquid extractions (Wasserscheid et al., 2000;Singh, 2005;Noda, 2000). Schiff base compounds are one of most prevalent mixed-donor ligands in the field of coordination chemistry (Li et al., 2009). As part of our program aimed at developing a novel functionalized ionic liquid, we now report the crystal structure of a novel ionic liquid-supported Schiff base (I).

Experimental
A mixture of the ionic liquid 1-(2-aminoethyl)-3-methylimidazolium hexafluorophosphate (4 mmol) and 2,4-dichlorobenzaldehyde (3 mmol) was stirred for 4 h at room temperature under solvent-free conditions. After completion ofthe reaction, ethanol (30 ml) was added to the reaction mixture, filtered off the solid product and washed with cold ethanol. The crude product was purified by recrystallization in ethanol/ethyl acetate(3:1 v/v). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of an ethyl acetate solution of the complex at room temperature.

Refinement
All H atoms were located in a difference Fourier maps and were refined as ridingatoms: C-H = 0.95-0.99 Å and with U iso (H) = 1.2 U eq (C).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.